This invention relates in general to flywheel clutch assemblies of the dry type i.e., clutch assemblies having pressure plates which are actuated to engage with and disengage from a drive plate connected with the flywheel of an engine.
Flywheel clutch assemblies of the type described are used to transmit torque from an engine to a drive shaft on a vehicle, such as a crawler tractor. In conventional clutch assemblies of this type the outer rim of the clutch drive plate is connected with the flywheel through a plurality of flexible links. One end of each flexible link is mounted on a drive pin projecting from the flywheel and the other end is bolted to the clutch plate by a shackle. The inner diameter of the drive plate is rotatably mounted about the drive shaft by means of a roller bearing assembly. A radial hole drilled through the drive plate and terminating with a zerk fitting is provided for lubricating the bearing. Axially extending holes are also drilled around the inner margin of the drive plate for connecting bearing shields and oil thrower plates.
Existing clutch assemblies of the type described have a number of limitations and drawbacks which can lead to serious mechanical problems in the drive train, premature failure of the clutch assembly, and attendant downtime and expense for maintenance, repair or even replacement of the clutch assembly. Among the problems which are encountered with these clutch assemblies is that of wobble in the drive plate which can arise from mounting of the drive plate on a center bearing about the drive shaft, which can be misaligned with the clutch elements. This wobble produces friction against the pressure plates during clutch engagement, thereby generating excessive heat which radiates out through the drive plate. Temperatures as high as 600.degree. F can be generated in many cases. This heat build-up destroys the lubricating properties of the grease in the bearing which can thereby fail, and the heat can cause fatigue cracks in the metal and ultimately failure of the clutch. The problem is compounded by the presence of stress risers in the drive plate, such as along sharp corners in the plate or along the radial grease hole or bearing end plate mounting holes. Excessive wobble in the bearing and clutch plate is also transmitted through the drive shaft to the transmission, which can be severely damaged in extreme cases. Moreover, because of the undesirable wobble action excessive forces are required for operating the handle to engage the clutch. A further problem is the requirement to periodically lubricate the center bearing. The zerk fitting on the clutch plate is in a relatively inaccessible position where it is difficult to lubricate so that mechanics tend to neglect this lubrication point. Such improper lubrication can lead to total failure of the bearing assembly which in turn requires expensive downtime for replacement.